Impulse translating apparatus



` Dec. 17, 1940. R, R. STEVENS 2,225,488

IMPULSE TRANSLATING APPARATUS Filed June 18, 19258 l v A /NVENTOR 46 lBV RRHH/ENS ATTR/VE V Patented Dec. 17, 1940 PATENToFFlcE IMPULsETaANsLArmG APPARATUS Ralph R. Stevens, Chatham, N. J., assigner to BellTelephone Laboratories, Incorporated, New York, N. Y., a corporation ofNew York Application June 18, 1938, Serial No. 214,460

14 claims.y

`'Ihis invention relates to telephone transmitters and more particularlyto telephone transmitters of the carbon granule type. r Telephonetransmitters of a type comprehended by this invention comprise, ingeneral, a xed or stationary electrode, a vibratile electrode, andmeans, which may include the electrodes, defining a chamber havingtherein a comminuted resistance varying material, such as carbongranules. When the vibratile electrode is actuated, as in accordancewith sound waves, the resistance material is agitated so that theresistance of the path between the two electrodes is varied and the ucurrent flowing in a circuit including these eleclJ trodes is modulated.

One object of this invention is to improve the modulating eiiiciency oftelephone transmitters. Another object of this' invention is to obtainsubstantial coniinement of the comminutedi resistance material betweenthe vibratile` and stationary electrodes in a telephone transmitterwhereby controlled resistance and uniform operating characteristics areobtained.

A further object of this invention is to concentrate the current intelephone transmitters in restricted paths between the electrodes.

In accordance with one feature of this invention, the means defining thechamber having the resistance material therein are so shaped that butrestricted portions of the material, principally that portion betweenthe electrodes, are agitated in accerdance with movements of thevibratile electrode and the tendency of the material to fall away fromthe region between the electrodes is reduced.

In accordance with another feature of this invention, the electrodes ofa telephone transmitter are provided with juxtaposed surfaces of suchform that the resistance material therebetween is subjected tosubstantially pure compressive forces when the vibratile electrode movestoward the xed electrode. 4

The invention and the foregoing and other features thereof will beunderstood more clearly and fully from the following detaileddescription with referene to the accompanying drawing in which:

Fig. 1 is a side view in section of a carbon granule type telephonetransmitter illustrative of one embodiment of this invention;

Fig. 2 is a partial top view, partly in section,

along line 2-2 of Fig. l, of the telephone transmitter shown in Fig. 1;

Fig. 3 is an enlarged diagrammatic view of a portion of the electrodesin the transmitter shown inFig`.1; and

' tioned. The diaphragm, which may be of sheet 10 metal, for example analuminum alloy, suiliciently rigid to vibrate as a whole, comprises afrustoconical portion I2 having an annular flange. I3 at one end, and aperipheral portion I4 which is provided with a stiiened edge, and issupported 15 between damping leaves I5, such as thin paper annull. Theperipheral portion I4 and the damping leaves I5 may be held in positionin the recess or groove in the frame by an annular plate I5 held againstthe frame I0 by a bent sheet 2 metal clamping member I1. If desired, a[moisture-prooi and protective screen I8 may be provided over the frontor concave surface of the diaphragm, the screen being clamped betweenthe frame I 0 and the plate I6. 25

,iiiixed to theV diaphragm and Vibratile therewith is an electrodehaving a cylindrical or sleeve portion I9 and a dished or conicalportion 20, the apex of which is within the cylindrical or sleeveportion I9. Preferably the concave surface of the conical portion 20 isplated, as with gold, to provide a low resistance and intimate contactbetween the electrode and the comminuted resistance material 2i, such ascarbon granules. The vibratile electrode may be provided with a ange 22adjacent one surface of the flange I 3 and with integral fingers or tabs23 bearing against the other surface of the flange I3 so that thevibratile electrode is securely aixed to the diaphragm and bodilymovable therewith. 40

A flexible aring or truste-conical closure member 24, for example ofsilk or the like, is clamped at one edge between the anges I3 and 22 andhas its other edge clamped against the flange II. 45 Seated upon theannular flange I I of the frame IIl is an annular insulating member 25having an inclined and curved inner wall 26 facing the diaphragm, theinsulating member 25 being coaxial with the vibratile electrode I9, 20.A second an- 50 nular insulating member 2l having an inclined I innerwall portion 28 is seated upon the insulating member 25 and positionedcoaxiallyr therewith.

. Seated in turn upon the insulating member 21 is a metallic memberhaving a cup-shaped'por- 55 tion 29 fitted on the member 21, a fiange30, a cylindrical portion 3I and a central portion 32 having a dished orconical surface 33a coaxial withthe conical portion 20 of the vibratileelectrode and having also a truste-conical surface 33h. The conicalsurface 33a may be of the same angle as the conical portion 20 or may beof a greater or smaller angle. 'I'he metallic member is insulated fromthe frame I0 by an annular insulating washer 34 seated upon the flange30 and having diametrically opposite tabs 35 fitted in notches or slots36 in the frame I0.

The central portion 32 is provided with a plurality of small apertures31 through which the y ring 39 threaded to the frame.

When the diaphragm `vibrates, as in accordance with sound wavesimpinging thereon, the electrode I9, 20 vibrates correspondingly so thatthe pressure upon the carbon granules between the dished or conicalsurfaces 20 and 33 is varied and the current iiowing in a telephonecircuit connected to the two electrodes is modulated. When the electrodeI9, 20 is thus vibrated, the conical portion 20 subjects the carbongranules to forces acting normal to the surface 20 at all pointsthereof. For example, as illustrated in Fig. 3, at two diametricallyopposite points a: and zi, the forces have the direction indicated bythe arrows F and F', i. e., normal to the inner surface of the conicalportion. 'I'he force F may be resolved into two components f1, parallelto the axis of the portion 20, and f2at right angles to this axis. 'I'heforce F' may be resolved into similar components f1 and f2'. Thecomponent forces 'f2 and fr', it will be seen, are of equal magnitudeand opposite in direction so that they tend to counterbalance eachother. The two components f1 and f1 likewise are of equal magnitude butof the'same direction, and force the carbon granules towardcorresponding points y and y1 on the conical surface 33a, the forcesexerted at these points being equal and represented by the parallelarrows F1 and F1'. The force F1 may be resolved into two components f4,normal to the surface 33a, and f3, parallel to this surface, and theforce F1' may be resolved into similar components f4' and fs'. Thecomponent forces f3 and fs' tendto cause a movement of the carbongranules outwardly along the surface 33a. However, if the angle 0between the surface 33a and the surfaces 33b and 28 is made 90 degreesor substantially 90 degrees, outward movement of the carbon granuleswill be substantially prevented.

The carbon granules outside of the cylindrical portion 20 are agitatedsomewhat by vibration of the flexible closure member 24. As will beapparent, because of the inclina-tion of the closure member 24 and thewalls 26 and 28, the forces thus produced will be toward the spacebetween the surfaces 30 and 33a, so that this body of carbon granulesproduces a pressure head serving to preventmovement of the granulesbetween the juxtaposed surfaces of the electrodes laterally outwardly.

Hence, it will be seen that the carbon granules lying between the/Juxtaposed surfaces of the electrodes are subjected to substantiallypure compressive forces when the diaphragm vibrates, so that a highdegree of modulation of the resistance in thev current paths betweenthese surfaces obtains.

Because of the form and disposition of the electrode surfaces, it willbe appreciated that the current between the electrodes is substantiallyconned to paths lying between the lateral extremities of the surface 20.'I'he electrical resistance of the structure, therefore, will be adirect function of the area. of the surface 20. Hence, good regulationof the resistance may be achieved, inasmuch as the area of the surface20 may be made relatively small and a suiciently high contact force`maintained between the granules and between the granules and thissurface to prevent overloading at normal speech pressures. v

The telephone transmitters shown in Figs. 4 and 5 are generally the samein construction as lthat illustrated in Fig. 1 and describedheretofore.V In the embodiment of this invention illustrated in Fig. 4,however, the electrodes are somewhat smaller and a single insulatingmember 4I! is provided, having a frusto-conical surface 4I defining themajor portion of the rear wall of the carbon granule chamber.

In the embodiment of this invention illustrated in Fig. 5, the innerwall of the single insulating member has two frusto-'conical wallportions 42 and 43, the latter of which extends at substantially rightangles to the surface 33a of the stationary electrode. They closuremember 24 may extend substantially normal to the cylindrical or sleeveportion I9 of the vibratile electrode. The insulating member, stationaryelectrode structure and insulating washer 34 may be clamped in positionby a locking ring 44 threaded to the frame I0 and having a bearingportion 45 engaging the washer 34.

If desired, a protective cover or grill 46 may be provided in front ofthe diaphragm I2 and secured to the frame by the clamping member I1.

Although specific embodiments of this invention have been shown anddescribed, it will be understood, of course, that various modiiicationsmay be made therein without departing from the scope and spirit of thisinvention as defined in the appended claims. l

What is claimed is:

1. A telephone transmitter comprising a diaphragm, an electrodeconnected to said diaphragm and vibratile therewith, said electrodehaving a central conical portion the apex of which is toward the frontsurface of said diaphragm, a fixed electrode having a conical portioncoaxial with and facing in the same direction as said first portion, awall member extending from the periphery of said fixed electrode and`flaring toward said diaphragm, a flexible wall member extending betweensaid first electrode and said first wall member, said wall members andsaid electrodes defining a chamber, and comminuted resistance materialsubstantially completely filling said' chamber.

2. A telephone transmitter comprising a vibratile element including adiaphragm, an electrode to the rear of said diaphragm, and a dish-shapediiexible annular member extending outwardly y from said electrode andiiaring away from said diaphragm, and a stationary element including asecond electrode and a wall member extending between said secondelectrode and the periphery of said annular member, said vibratile andstationary elements defining a chamber, and comminuted resistancematerial substantially completely lling said chamber, said electrodeshaving juxtaposed surfaces deiining a restricted passageway.

3. A telephone transmitter in accordance with claim 2 wherein said wallmember is substantially frusto-conical and flares toward said diaphragm.

4. A telephone transmitter in accordance with claim 2 wherein saidjuxtaposed surfaces are central with respect to the respectiveelectrodes, coaxial and substantially conical, said surfaces tapering inthe same direction and the apices thereof being toward the front of saiddiaphragm. y

5. A telephone transmitter comprising a diaphragm, means to one side ofsaid diaphragm deiining a chamber, and comminuted resistance materialsubstantially completely filling said chamber, said means comprising anelectrode vibratile with said diaphragm and having a cylindrical portionand a central, continuous dished portionv within saidi cylindricalportion, the concave surface -of said dished portion facing away fromsaid one side of said diaphragm, and a second electrode having a surfaceopposite and ing away from said diaphragm, a second electrode having asurface in juxtaposition to the inner surface of said dished portion andconforming thereto, means including said electrodes defining a chamber,and comminuted resistance material in said chamber, said means includingalso an insulating member having a surface extending from the peripheryof said second surface and inclined toward said nrst electrode.

8. A telephone transmitter comprising a diaphragm, an electrode coupledto said diaphragm and vibratile therewith, said electrode having acentral portion dished toward said diaphragm, a second electrode havinga surface opposite and substantially conforming to said portion, meansincluding said portion and surface defining a chamber, and comminutedresistance material in said chamber, said means including also aflexible member extending from the peripheryof said rst electrode andflaring away from said diaphragm.

9. A telephone transmitter comprising a diaphragm. an electrodevibratile with said diaphragm, a stationary electrode, said electrodeshaving juxtaposed surfaces defining a restricted passageway and dishedtoward said diaphragm, means including said electrodes defining achamber, and comminuted resistance material in said chamber, said meansincluding also an insulating wall member aring away from said diaphragmand a second insulating wallmember inclined toward said diaphragm.

10. A telephone transmitter comprising a vibratile electrode having adished portion, means defining a chamber with the concave surface ofsaid dished portion of said electrode, and comminuted resistancematerial in said chamber, said means including an electrode having asurface in juxtaposition to and dished in the same direction as saidportion, and including also an insulating member having a wail extendingfrom adjacent the periphery of said second surface, flaring toward saidfirst electrode and at substantially right angles to said secondsurface.

ll. A telephone transmitter comprising a vibratile electrode having acentral conical portion,

means defining a chamber with the concave surface of said portion, andcomminuted resistance material in said chamber, said means including asecond electrode having a conical surface in juxtaposition to saidportion and substantially uniformly spaced therefrom, an insulatingmember having a frusto-conical wall extending from said second surfaceand iiaring in the direction of said first electrode, and a exiblemember extending from the periphery of said vibratile electrode to saidmember.

12. A telephone transmitter in accordance with claim 11 wherein saidflexible member is frustoconical and flares toward said frusta-conicalwall.

13. A telephone transmitter comprising a vibratile electrode having aconical portion, means defining a chamber with said electrode,comminuted resistance material in said chamber, said means including aflexible member extending out- Wardly from the periphery of saidvibratile electrode, a second electrode having a conical surface coaxialwith and equally spaced from said portion, and a member having a wallportion extending inwardly from the periphery of said ilexible memberand obliquely with respect to said flexible member and having a secondwall portion extending from the periphery of said conical surface and atsubstantially iight angles thereto.

14. A telephone transmitter comprising a diaphragm, an electrode coupledto said diaphragml and vibratile therewith, said electrode including acylindrical portion extending normal to the central portion of thediaphrgam and coaxial with said diaphragm and including also a conicalportion within said cylindrical portion and having its periphery joinedthereto, the inner surface of said conical portion facing away from saiddiaphragm, a second electrode coaxial with said first electrode having aconical surface opposite said first surface and conforming thereto,means including said electrodes defining a chamber, and comminutedresistance material substantially completely filling said chamber, saidmeans including also a fixed insulating member having a dished surfacecoaxial with said electrodes, extending from the periphery of saidsecond electrode and having its elements inclined toward said diaphrgam,and including also a flexible frusto-conical insulating member coaxialwith said electrodes and having its smaller end joined to saidcylindrical portion and its larger end joined to said dished surfaceadjacent the periphery thereof, the inner surface of said frustoconicalflexible member facing toward said second electrode.

RALPH R. STEVENS.

